To say hello, of course. Puppies are social creatures and happy and excited to greet just about anyone! Jumping, leaping and bouncing are ways your dog shows affection and receives attention. When a puppy is very young, we usually sit on the floor, let them wiggle into our laps and allow them to lick and nuzzle up close to our face. This is OK because we are down at their level.
Other commands can be substituted for ‘sit’ if you prefer, such as ‘stay’ or ‘down.’ However, if your dog simply gets too excited to execute these commands properly (as is often the case, especially with puppies) try diverting their attention elsewhere. Ask them to go find their ball, or a favorite toy, as a way to distract them and expend some energy. And, as always, reward the good behavior with praise.
Teach your puppy a conflicting behavior such as “fetch your ball.” She can’t jump up if she’s running to bring you her ball or favorite toy. Just the name of a special game or toy—“go get your bear!”—can change the dog’s focus and redirect the behavior long enough for you to evade the jumping. With enough repetition, your puppy will begin to associate your home-coming with “go fetch” instead of jumping up.
Make sure other family members and visitors understand this command, as well. It is crucial that your dog understand that all family and visitors are above his rank in the pack. Otherwise, he will lash out and try to assert himself on everyone. While using the Off command may not be appreciated by most visitors, but it is more important that a dog has a good greeting manner with all people. A little effort on everyone's side makes your dog disciplined and docile.
When a dog jumps on a human of its own free will, it is not "greeting" the human, it is asserting its dominance over the human; it is the dog communicating that it is alpha and/or wishes to own/control the human. A subordinate would never dream of running over and jumping on the alpha dog of the pack. Space is respect and lower members of the pack respect the higher members. If your dog jumps on humans, it does not respect them. Note: when a young puppy jumps on humans it is sometimes its attempt to reach one's face. Puppies need to be taught not to jump up on humans as this behavior will manifest into other meanings as the puppy grows up into an adult dog.